1. Field of the Invention
The present invention relates to a rotary drive apparatus of a type wherein a magnetic force is generated between a rotor and stator for reciprocatively moving the rotor. The apparatus is adapted for use as a compact rotary type actuator utilized for operating, for example, a rotary valve.
2. Description of the Related Art
Known in the prior art is a rotary apparatus including a rotor made of a magnetic material of an elongated shape with oppositely magnetized ends yokes of C-shape arranged astride the rotor, permanent magnets connected to the yokes, and a coil for magnetizing the rotor so that the ends of the rotor are oppositely magnetized (see Japanese Unexamined Patent Publication No. 58-148408). This rotary apparatus is adapted for use for driving a self-holding type relay apparatus. Each of the yokes has a pair of ends which face the ends of the rotor and which are magnetized by means of the corresponding permanent magnet. The ends of one yoke faces with the ends of the other yoke via the respective ends of the rotor. Due to this construction, flows of magnetic flux are generated between the rotor, yoke, and the permanent magnets, causing the rotor to be rotated for a limited angle between the two positions defined by the distance between the ends of the yokes.
The above-mentioned prior art suffers from the drawback that the yokes are required to transmit the magnetic flux for generating a closed loop of the flow of the magnetic flux causing an increase in the number of parts for constructing the apparatus and resulting in a complicated structure thereof.